1. Field of the Invention
The present invention relates to an oil pump built in a closed type compressor for supplying a lubricant to sliding portions of the compressor.
2. Description of the Related Art
A typical upright closed type compressor such as scroll type compressors, rotary type compressors and the like is housed by a closed housing which is divided into two parts or upper and lower portions including a compressing mechanism and an electric motor, respectively. In such an arrangement, a rotary shaft of the electric motor is coupled with the compressing mechanism so that the compressing mechanism may be driven by the electric motor.
In general, in such closed type compressors, an oil pump is built in at a lower end of the rotary shaft. The oil pump sucks a lubricant oil reserved in an inside bottom of the closed housing to supply the oil to sliding portions of the compressing mechanism through an oil supplying channel formed inside the rotary shaft.
FIGS. 4 and 5 show a configuration of a conventional oil pump provided for the closed type compressor.
In the figure, reference numeral 1 designates a closed housing. Designated at 2 is a cylinder which is disposed in the inside bottom of closed housing 1. The cylinder 2 has a recess portion 2a defining a cylinder chamber 3. The cylinder 2 is integrally formed with a stay 4 whereby cylinder 2 is fixed to closed housing 1. Recess portion 2a is enclosed by a thrust plate 5 and a cover plate 6 attached to cylinder 2 to form the cylinder chamber 3.
A rotary shaft designated at 7 is inserted at a lower end thereof into cylinder 2. The lower end of the rotary shaft 7 is positioned inside cylinder chamber 3 and formed with an eccentric shaft 8. Designated at 9 is an annular rotor disposed inside cylinder chamber 3. The rotor 9 is fit rotatably on the periphery of eccentric shaft 8. The peripheral surface of the rotor comes into contact with the inner peripheral surface of cylinder chamber 3 to limit the space of cylinder chamber in a crescent shape.
A projection 10 in a form of blade extending radially is integrally formed on the periphery of rotor 9. The projection 10 is inserted slidably into a slot 11 radially formed on the inner peripheral surface of cylinder chamber 3. Projection 10 partitions cylinder chamber 3 into an oil feeding chamber 3a and an oil discharge chamber 3b while inhibiting rotor 9 from rotating. It should be noted that rotor 9 is substantially round or of a circle except the projection 10.
Formed in cover plate 6 is a sucking hole 12 which is positioned below oil feeding chamber 3a of the cylinder chamber 3. The sucking hole 12 communicates with the inside bottom of closed housing 1. Provided for thrust plate 5 is a sucking port 13 which communicates sucking hole 12 with oil feeding chamber 3a of cylinder chamber 3.
An ejecting passage 14 is provided in a cover plate 6. Provided on thrust plate 5 are an ejecting port 15 and a communicating hole 16. This ejecting port 15 communicates ejecting passage 14 with oil discharge chamber 3b of cylinder chamber 3 while the communicating hole 16 communicates ejecting passage 14 with an oil supplying channel 17 of rotary shaft 7. The oil supplying channel 17 is formed axially inside rotary shaft 7 from the bottom to the top. The inside bottom of closed housing 1 reserves lubricant.
Advantages of this oil pump are that damages to the rotor can be prevented and that the pump can be formed with a less number of parts since projection 10 is integrally formed with rotor 9.
In the thus constructed oil pump, as rotary shaft 7 is rotated by the electric motor, eccentric shaft 8 eccentrically rotates in a direction shown by the arrow in FIG. 5. This rotation causes eccentric shaft 8 to urge rotor 9 so that the rotor 9 revolves with its outer peripheral surface abutting the inner peripheral surface of cylinder chamber 3 in a line contact (sharing a line in the contact therebetween). Accordingly, as rotor 9 revolves, the volumes of oil feeding chamber 3a and oil discharge chamber 3b vary relatively, or one increases and the other decreases.
As the volume of oil feeding chamber 3a increases, the lubricant oil reserved in the inside bottom of closed housing 1 is sucked into oil feeding chamber 3a by way of sucking hole 12 of cover plate 6 and sucking port 13 of thrust plate 5. 0n the other hand, as the volume of oil discharge chamber 3b of cylinder chamber 3 decreases, the lubricant existing in oil discharge chamber 3b is pressurized to be ejected from ejecting port 15 of thrust plate 5. The ejected lubricant passes through ejecting passage 14 of cover plate 6 and communicating hole 16 of thrust plate 5 and is fed from the lower end of rotary shaft 7 into oil supplying channel 17. The lubricant is transported through the oil supplying channel 17, flowing out from the upper end of rotary shaft 7, to be delivered to and lubricate sliding portions in the compressing mechanism. After the lubrication, the lubricant flows down inside closed housing 1 to be re-collected in the bottom.
By the way, in the conventional oil pump, angled portions 18 formed on both sides of the opening of slot 11 disposed in the inner peripheral surface of cylinder chamber 3 in cylinder 2, are beveled forming slanting faces. More specifically, as the projection 10 of rotor 9 reciprocates slidingly inside slot 11, the root of projection 10 interferes with the angled portions 18 on both sides of the opening of slot 11. For this reason, the angled portions 18 are likely to be cracked or receive any other damages. To deal with this, the angled portions 18 on both sides of the opening of slot 11 is beveled in order to avoid any interference of the root of projection 10 with angled portions 18, whereby the angled portions are prevented from being cracked and damaged.
In general, a cylinder 2 is composed of metallic materials, and cylinder chamber 3 is formed by machining the cylinder 2 with a milling machine. Accordingly, angled portions 18 on both sides of the opening of slot 11 are also beveled by the machining process using the milling machine.
It is a very troublesome and difficult process, however, to bevel the narrow angled portions 18 on both sides of the opening of slot 11 by machining. Besides, the machining process leaves burrs on the beveled portions, so that the worker must remove the burrs after the machining. The necessity of the removal of burrs increases the number of steps for manufacturing the cylinder to thereby increase manufacturing costs.